The present invention relates, in general, to an image signal processing system for recording or reading an image signal to or from a storage medium and, more particularly, to an image signal processing system having a mode discriminating device for determining the present mode of the system. The mode discriminating device includes a cam switch and connecting element formed in association with a voltage divider, which divides a power supply voltage according to the position of the connecting element and outputs a signal whose voltage value is indicative of the present mode of the system.
A conventional mode discriminating device, which is often used in an image signal processing system, includes several mode discriminating ports arranged at predetermined positions of a cam switch in accordance with different modes of the system. In such a device, the modes of the system are discriminated on the basis of electrical signals produced at the mode discrimination ports by a rotating cam switch.
For example, assuming that three mode discriminating ports are provided in the cam switch, if the electrical signals produced at the mode discriminating ports are at a high, high, and low level, respectively, then a first mode (e.g., stop) is discriminated. On the other hand, if the signals are at a logic low, high, and low level, respectively, then a second mode (e.g., play) is discriminated.
A mode discriminating technique as described above is disclosed in U.S. Pat. No. 5,061,848, entitled "NON-CONTACTING ROTARY TYPE MODE SWITCH FOR MAGNETIC TAPE RECORDING DEVICE", in which a non-contacting rotary type mode switch having several reflecting pieces and light reflecting sensors is employed to discriminate the current mode of the system. That is, each of reflecting pieces is formed on a corresponding one of multiple concentric tracks which are defined on a back surface of a mode switch gear, and the light reflecting sensors are formed on an upper surface of the switch body to read the rotating mode of a cam gear. The system includes a means for emitting light and light receiving means for detecting the light reflected from the reflecting pieces.
However, in a conventional mode discriminator, which employs mode discriminating ports, the ports must be contacted correctly with high mechanical accuracy. Further, even if a microcomputer is employed to recognize data produced from the mode discriminating ports, erroneous data recognition will occur. Moreover, the construction of the device is quite complicated like, for example, the device described in the aforementioned U.S. Pat. No. 5,061,848.